Early last November, small but active Comet Hartley 2
(103/P Hartley) became the
imaged close-up by a
from planet Earth.
the solar system with a 6 year
orbital period, Hartley 2 is is making
astronomical headlines again, though.
Space Observatory measurements indicate that the water
found in this comet's thin atmosphere or coma has the same ratio
of the hydrogen
deuterium (in heavy water)
as the oceans of our fair planet.
Hartley 2 originated in the
distant Kuiper Belt,
a region beyond the orbit of Neptune that is a reservoir
of icy cometary bodies and dwarf planets.
Since the ratio of deuterium is related to the solar system
environment where the comet formed, the Herschel results
indicate that Kuiper Belt comets could have
contributed substantial amounts of water to Earth's oceans.
Comet Hartley 2 appears in
this starry skyscape from last November
sporting a tantalizing greenish coma appropriately sailing through the
Below the comet are open star clusters M47 (right) and